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Ten questions, ten answers, know the Vertical mill

Date:2019-06-28 10:01 Source:未知Views:

Vertical mill is a generally accepted energy-saving high-efficiency grinding equipment in the world. The vertical mill has been widely used in the regrinding and fine grinding operation of non-ferrous metal, ferrous metal and non-metal ore because of its characteristics such as tower structure, small installation area, low dynamic load and small vibration. We know the vertical mill through ten times. In the later article, we will introduce more about the relevant knowledge points of the vertical mill.

1. Why is the vertical mill energy efficient?

Large vertical mill is mainly composed of cylinder, spiral agitator, transmission device and frame. The vertical structure of the vertical mill can improve the grinding energy efficiency. In the vertical mill, the spiral agitator rotates slowly, and the velocity does not fluidize the medium and does not cause gravity settlement. The vertical structure is beneficial to the internal micro-classification of particles and reduces overwear, so the efficiency is improved.

On the other hand, the main force of the vertical mill is friction grinding, which does not need a large ball. Therefore, the mill can add relatively small medium, so that its grinding area is three times higher than that of the ball mill with the same load.

2. How does the grinding effect of the vertical mill come into being?

The grinding effect of vertical mill mainly occurs in two areas, one is the area on the spiral blade, and the other is the annular area composed of the outer edge of the spiral blade and the inner wall of the cylinder. There are three main types of grinding and stripping in two areas:

2.1 grinding of grinding media;

2.2 Intergrinding between the helical blade and the grinding medium;

2.3 The grinding and peeling between the inner wall of the cylinder and the grinding medium.

3. The reason of vibration of vertical mill?

3.1 Vibration caused by insufficient preheating.

If the preheating is insufficient, some of the heat in the input mill will be absorbed by the grinding body, resulting in insufficient heat exchange, breaking the heat balance, increasing the friction force on the grinding disk, decreasing the mobility, caking the plate of the material bed, decreasing the powder yield of the material rolled by the roller, and unable to be taken off the grinding disk by the hot air, resulting in the fluctuation of the material bed and vibration.

3.2 Vibration caused by insufficient feed volume.

The output of vertical mill can be adjusted in a certain range, but when the feed quantity is too low, the moisture in the mill decreases, the absorbed heat is lower than the heat supply, the material is dried quickly, the plasticity of the material bed is reduced, and it is not easy to form a stable material layer and cause vibration.

3.3 Vibration caused by overgrinding.

The improvement of raw material grindability, the high grinding pressure and the high speed of separator may lead to the increase of suspended fine material above the grinding disk, the increase of dust gas density, the increase of collision probability between particles, the interference of the powder selection process of separator, the material that reaches the fineness standard can not be brought out of the vertical mill, the material balance is broken, and the proportion of fine material on the bed increases, causing vibration.

Other causes of vibration: the vibration measuring element is out of order; the roller skin is loose and the lining plate is loose; the feeding amount is too large, too small or unstable; the air volume of the system is insufficient or unstable; the grinding pressure is too high or too low; the speed of the powder separator is too high; and the nozzle ring is blocked seriously, and the like.

4. What are the advantages of vertical mill compared with ball mill?

5. What is the influence of the velocity field in the classification area on the classification performance of the grinding separator?

The speed gradient of the grading zone has a great influence on the grading performance of the powder separator, and the speed gradient of the grading zone is higher than that of the general assembly, so that the stress of the particles is changed, the movement track of the particles is deviated, and the powder selection precision and the powder selection efficiency of the powder selection machine are further reduced.

The average velocity of the cage classification area of the straight blade structure is low and there is a large velocity gradient, and the classification performance is lower. The velocity field of the cage classification area of Z-shaped and streamline blade structure is better, and the classification performance is also higher. The use of Z-shaped and streamline blade structure is beneficial to increase the velocity size of the classification zone and reduce the velocity gradient, and improve the classification accuracy and classification efficiency. Considering the difficulty of streamline blade machining and the cost consideration in actual production, it is suggested that Z-shaped blade structure should be used.

6. what are the common faults of slag vertical mill reducer?

6.1 torque signal detection reducer monitoring failure.

Each component in the vertical mill equipment, especially the important part, has its own unique engagement frequency and rotation frequency, which provides the theoretical basis for determining whether the various frequencies of the component are normal or not and whether the fault occurs through the torque signal.

The running state and important parts of slag vertical mill reducer are detected by torque detection system, and the corresponding torque curve spectrum is obtained at the same time. Through the analysis of torque curve and spectrum, it is checked whether there is obvious regular vibration of the reducer, if so, the object and position of the fault are preliminarily determined, and then the fault is further analyzed, including the damage degree of the parts, the wear situation, the changing trend and so on. And according to the torque to provide testing information to make appropriate maintenance arrangements, timely troubleshooting.

6.2 Detection and diagnosis of bearing faults.

Disassemble the vertical mill reducer and carefully inspect all the bearings of the planet at all levels. If it is found that some or all of the bearings are damaged, such as the bearing ball or inner ring, the outer ring is prone to serious peeling, pitting, holder fracture, severe wear, and many small, sheet-shaped iron chips on the planet frame, it can be determined that the bearing of the reducer has serious wear and damage. In the process of testing, if corrosion is found on the planetary carrier or bearing surface at all levels of the reducer, the gear lubricating oil needs to be sampled for detection. If the water content of the lubricating oil increases, it indicates that there is water seepage into the lubricating oil, resulting in corrosion of the reducer bearing and planetary carrier. And the bearing of the speed reducer is caused to be damaged.

7. The reason why the wear-resistant layer of the roller sleeve of the slag vertical mill

At present, the wear-resisting technology of the domestic professional manufacturers has been very mature, and the main problems may be concentrated on the wear-resistant layer which is caused by the structure to fall off. The possible reason is that the structure of the casting matrix is different, the thickness of the wear-resistant layer is different, and the wear-resistant layer is peeled off or the wear-resistant layer is quickly ground out of the groove due to the vibration of the grinding machine during use.

The size of the joint between the body and the wear-resistant layer is too low, which causes the thickness of the wear-resistant layer to be too thick. The joint part of the body and the wear-resistant layer is too high, so that the thickness of the wear-resistant layer is too thin, and the wear-resistant layer in use can be quickly abraded out of the groove so as to damage the body, so that the grinding of the mill is not sufficient, the yield of the mill is influenced, and the repair is difficult.

8. what is the reason for the foaming of lubricating oil for vertical grinding roller bearings?

There are many reasons for foaming of oil products, which can be divided into two categories: oil products themselves and external factors.

The factors of the oil product include: the consumption of the anti-foaming agent in the oil; the oxidation and deterioration of the oil.

External factors mainly include: equipment and use and external pollutants.

the oil return hole is too close to the oil hole, the volume of the oil tank is too small, the oil circulation speed is too fast, the oil product does not have a certain time to release the foaming caused by the air, and the oil pump is leaked, The foaming and the like caused by the excessive air brought into the system, and the like, and belongs to the problems of equipment and usage. Environmental pollution substances: alkaline substances, soap substances; porous dust; the materials can adsorb anti-foaming agents and the like.

9. What is the cause of the roller bearing failure of the vertical mill?

General bearing failure general performance:

9.1 Contact fatigue failure. The formation process and the consequences are: the pitting of the pitting and the deep-layer spalling of the shallow layer.

9.2 Wear failure. The formation process and consequences are as follows: the change of wear shape and the increase of fit gap and the change of working surface, the lubrication function of lubricant is lost, and the rotation accuracy of bearing is lost.

9.3 fracture failure. It is mainly affected by overload and defect. Overload fracture occurs when the load exceeds the strength limit. The defects of bearing parts, such as microcracks, shrinkage holes, bubbles, large pieces of foreign sundries, overheated microstructure and local burns, will also cause fracture at the defects when they shock and overload or vibrate violently.

9.4 bearing clearance change failure.

The joint action of internal and external factors leads to the change of fit clearance, which leads to the reduction of bearing accuracy, resulting in the phenomenon of "biting". External factors mainly refer to excessive interference, inadequate installation, expansion caused by temperature rise, instantaneous overload, etc., and the internal factors are mainly retained Austenite and residual stress in unstable state.

The loss of tapered roller bearings may be due to bearing quality problems, bearing assembly problems, use problems or seal damage, ash intake.

10. the reason for the low output of vertical mill?

The grinding mechanism of the vertical mill is very complicated, and various parameters such as the structure parameters of the vertical mill have the spiral diameter, the pitch size (the screw lift angle size), the operating parameters have the size of the grinding medium, the medium filling rate, the running speed and the like, and the grinding efficiency can be influenced.

11. the reasons for the low output of vertical mill are as follows:

11.1 Wear of roller and disc liner

11.2 Wear of retaining rings

11.3 Wear of nozzle ring

11.4 Properties of grinding materials

11.5 system air leakage

In addition to the above factors, there are many factors that affect the output of vertical grinding, such as material segregation caused by mixture structure, air volume control, hot air temperature control, proportioning control and so on, which will affect the output of vertical grinding. In the actual production, it should be analyzed according to the specific situation of our factory, aiming at solving the problem. Whether the vertical mill can run smoothly and high speed has a direct impact on the grinding ability of the mill. In the process of vertical grinding, it is necessary to check and repair the vertical mill in time so as to make the mill run smoothly and high speed and give full play to the best grinding ability of the mill.


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